1. Field of the Invention
This invention pertains to the field of treating substrates with a treating medium. More particularly, the present invention is directed to an apparatus and method for turbulently applying a treating medium onto a substrate to more effectively apply the medium onto and throughout the substrate in a more controlled manner.
2. Discussion of Related Art
Man-made fibers are generally formed by extruding a spinning solution through a spinnerette to form a tow made up of a number of individual filaments, usually at least about 3,000 filaments, or more. In the production of these fibers, it is usually necessary to subject the tow of fibers to some kind of treatment with a liquid treating medium at some state in the manufacture of these fibers.
For example, the tow of fibers is generally washed with water for the purpose of removing a spinning solvent. Alternatively, a lubricating agent, a sizing agent, or a finishing agent may be applied to the fibers during their manufacture and as a last step before being wound onto a creel in order to improve their handleability and processability during and after manufacture. So too, the treating medium may comprise a dye to color the fibers, a washing medium to remove excess dye after a dyeing operation, or a chemical agent to modify the physical and/or chemical properties and behavior of the fibers.
Similarly, a woven cloth may also have need for being treated with a liquid treating medium during its manufacture at a textile mill. Thus, the steps of washing, dyeing, adding a finishing agent, an antistatic agent, ect. may also be applied to such a cloth as well. As used herein, the term "substrate" is meant to include one or more fibers in the form of a tow, or in a form where the fibers have been worked to form a cloth, such as, a woven or knitted fabric etc.
Various means have been employed in the prior art for applying a treating medium onto a substrate such as a tow of fibers or a fabric.
In one system, the substrate merely enters and leaves a bath containing the treating medium. For example, in some wet spinning operations, a freshly spun synthetic fiber tow is passed through one or more baths of hot water to remove the residual solvent from the filaments. A major disadvantage of this process is that it is inefficient. This inefficiency stems from the fact that circulation of the hot water around and through the moving tow is generally poor.
In another system, such as the one described in U.S. Pat. No. 3,791,788, the substrate passes through a confined zone having elaborate deflecting surfaces provided therein as the treating medium is applied. While the confined zone may aid in the effectiveness of applying the treating medium onto the substrate, this system may suffer from the disadvantage that the treating medium is applied in a manner which does not provide a satisfactory degree of agitation of the fibers within the substrate. As a result, all of the surface area of the fibers may not thoroughly be subjected to the effects of the treating medium and, most importantly, not all the fibers will have been separated from one another, i.e, deagglomerated. The treating medium is generally applied by flowing through a channel which is transverse to the direction of substrate travel. As a result, the flow pattern of the treating medium and the manner in which it impinges upon the substrate is such that it may not be effective in getting at the surface of each fiber.
In yet another system, the treating medium is applied by means of spray jets as the substrate passes in close proximity. This system of application is meant to overcome yet another disadvantage associated with each of the first two applicating systems noted above. In particular, one of the primary concerns in the production of synthetic fibers in the form of a tow is the sticking of one fiber to another which results in a decrease in the overall tensile strength of the tow. In contrast to the baths or confined treatment zones discussed above, the application of the treating medium by means of spray jets is generally able to disentangle and unstick any fibers that are joined together, particularly when the treating medium employed is an oiling agent or a finishing agent, due to the direct and forceful impingement of the fibers with the treating medium. However, when the substrate is allowed to simply freely pass past the spray jets, there is no real control as to the amount of impingement upon the fibers. As a result, the fibers usually wind up being stretched, even to the point of breakage. Such stretching and/or breaking of the fibers within a tow will generally undesirably affect its strength characteristics.